As laser processing becomes more capable and economical, more and more parts are being machined using laser processing rather than mechanical, chemical or electrical processing. One particular type of material that is adapting favorably to laser processing is glass and glass-like materials. Processing of glass or glass-like articles using a laser are discussed in two co-pending applications assigned to the assignee of this application, namely U.S. patent application Ser. No. 12/336,609 METHOD FOR LASER PROCESSING GLASS WITH A CHAMFERED EDGE and 61/164,162 GLASS MACHINING WITH PRECISELY TIMED LASER PULSES, both of which are included by reference.
During machining of glass articles, it's necessary to make sure that the correct side of the part to be machined is presented to the processing head. This is important since the machining operations are typically not symmetric with respect to the top and bottom of the article, therefore the article must be correctly oriented in order to be properly machined. This may not be trivial if the part in question has two or more sides that look sufficiently similar to make visual identification of the correct processing side difficult. An example is an essentially flat “sheet like” part that can be placed with either side up into the system. Typically, part manufacturers will try to ensure that there is no ambiguity as to which side of a part is the “processing side” by either marking this side with a unique identifier (such as a label, bar-code, etc.) which can be verified either by an operator or an automated machine vision system, or by drilling into the part fixturing holes that make it impossible to place the part in the processing area in any orientation other than the correct one.
Some articles, however, do not lend themselves to being oriented in this fashion. Marking or labeling the parts adds time and expense to the manufacturing process. Some articles do not lend themselves to adding part fixturing holes or features since they would detract from the finished product. A method of identifying which side of the part is uppermost is useful to prevent the article from being loaded improperly. In the case where the machine is loaded automatically without human intervention, a method of identifying the orientation of loaded articles can prevent the machine from processing the article on the wrong side.
There is therefore an ongoing need for a method and apparatus for identifying the orientation of a transparent article loaded into a laser processing machine.